speedball help the upper right LED does not light [resolved]

Plumbum · 1680

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Offline Plumbum

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on: October 20, 2018, 12:58:05 AM
Hello! the upper right LED does not light
Terminal Voltage (DC)
OA 71V
IA 185V
B-A / B 0V
IB 185V
OB 57V
« Last Edit: October 21, 2018, 07:20:49 AM by Paul Birkeland »


Offline Paul Birkeland

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Reply #1 on: October 20, 2018, 05:49:55 AM
This is on the smaller PC board?

Do both LEDs remain lit on the 9 pin socket when you do this test (no need to mess with them either way).

Was the amp working OK prior to installing this board?

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Plumbum

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Reply #2 on: October 20, 2018, 07:21:47 AM
This is on the smaller PC board?  - Yes
Do both LEDs remain lit on the 9 pin socket when you do this test (no need to mess with them either way).- Yes
Was the amp working OK prior to installing this board? - Yes
I assembled the speedball completely, everything works, not only one light this diode


Offline Paul Birkeland

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Reply #3 on: October 20, 2018, 07:22:49 AM
Quote from: Plumbum on October 20, 2018, 12:58:05 AM
OB 57V
This means the front PC board isn't working.  Can you pull the rear PC board out and recheck this voltage?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Plumbum

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Reply #4 on: October 20, 2018, 07:41:13 AM
Foto:


Offline Paul Birkeland

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Reply #5 on: October 20, 2018, 07:49:13 AM
You have a backwards transistor on your small PC board.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Plumbum

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Reply #6 on: October 20, 2018, 08:07:39 AM

PN2907A transistors, 2N2222A transistors,MJE-350 transistors, TIP-50 transistors

which to choose?


Offline Paul Birkeland

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Reply #7 on: October 20, 2018, 08:35:36 AM
Your small PC board has MJE350 and PN2907 transistors on it.  One of them is backwards.  It's visibly obvious because the shape of the transistor is inconsistent with the white outline on the PC board where it mounts.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Plumbum

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Reply #8 on: October 20, 2018, 10:05:53 AM
I broke the transistor... pn2907a, there are analogues? I'm in Russia


Offline Plumbum

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Reply #9 on: October 20, 2018, 10:08:46 AM
Yes! I am very grateful to you, thank you very much!


Offline Plumbum

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Reply #10 on: October 20, 2018, 10:11:35 AM
 :)


Offline Paul Birkeland

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Reply #11 on: October 20, 2018, 10:12:11 AM
You'll probably be able to make more sense out of this than I can, but here is a potential source:

http://www.platan.ru/cgi-bin/qwery_i.pl?code=PN2907

The prices seem pretty high, but shipping should be reasonable.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Plumbum

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Reply #12 on: October 21, 2018, 01:17:14 AM
all perfectly!!! Thank you very much!


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